Identification of QTLs for Yield and Yield Related Traits under Reproductive Stage Drought Stress

Reproductive-stage drought stress can substantially reduce rice productivity, making the identification of drought-responsive loci relevant to breeding. This study aimed to detect phenotypic variation and identify QTLs associated with yield and yield-related traits under reproductive-stage drought stress. Drought stress is one of the major challenges in agriculture, particularly in rice production, and has significant negative impacts on rice growth and yield. Reproductive-stage drought stress is an important yield-reducing factor in rain-fed rice production. Therefore, identifying grain yield-related quantitative trait loci (QTLs) during the reproductive stage may provide additional benefits for marker-assisted breeding. This experiment was carried out at the Department of New Genetics, Yezin Agricultural University, Nay Pyi Taw, from August 2025 to January 2026 using a randomized complete block design (RCBD) with three replications under two conditions: 100% field capacity (control) and 50% field capacity (drought). Significant differences were observed in yield and yield-attributing variables. Eleven QTLs were identified for six traits: plant height, panicle length, days to 50% flowering, spikelets per panicle, filled grain percentage, and 1000-grain weight. Two QTLs for plant height were identified on chromosomes 1 and 5, with R2 values of 44.58% and 9.79% and LOD values of 11.12 and 3.68, respectively. The QTL for panicle length, qPL5, was identified on chromosome 5, with an R2 value of 16.25%. Four QTLs (qDTF1.1, qDTF1.2, qDTF6, and qDTF10) were identified on chromosomes 1, 6, and 10 for days to 50% flowering. One QTL each was identified for spikelets per panicle and filled grain percentage (qSPP5 and qFGP8, respectively). For 1000-grain weight, two QTLs, qTGW1 and qTGW3, were identified on chromosomes 1 and 3. These QTLs may be useful for marker-assisted breeding of rice with improved resilience to climate change, particularly drought.